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Assembly Source File | 1990-11-05 | 32.2 KB | 770 lines

;EXECWSWP.ASM ; Swap memory and exec another program, keeping child process's video ; output to a specified portion of the screen ; Copyright (c) 1988,1990 TurboPower Software ; May be used freely as long as due credit is given ; ;----------------------------------------------------------------------------- DATA SEGMENT WORD PUBLIC EXTRN BytesSwapped:DWORD ;Bytes to swap to EMS/disk EXTRN EmsAllocated:BYTE ;True when EMS allocated for swap EXTRN FileAllocated:BYTE ;True when file allocated for swap EXTRN EmsHandle:WORD ;Handle of EMS allocation block EXTRN FrameSeg:WORD ;Segment of EMS page frame EXTRN FileHandle:WORD ;Handle of DOS swap file EXTRN SwapName:BYTE ;ASCIIZ name of swap file EXTRN PrefixSeg:WORD ;Base segment of program EXTRN NewInt21Addr:WORD; ;Hold addr on our int 21 handler DATA ENDS ;----------------------------------------------------------------------------- CODE SEGMENT WORD PUBLIC ASSUME CS:CODE,DS:DATA PUBLIC ExecWinWithSwap, FirstToSave PUBLIC AllocateSwapFile, DeallocateSwapFile PUBLIC DefaultDrive, DiskFree PUBLIC EmsInstalled, EmsPageFrame PUBLIC AllocateEmsPages, DeallocateEmsHandle PUBLIC InstallInt21, RestoreInt21, CheckCursor PUBLIC UpdateCsVars ;----------------------------------------------------------------------------- FileAttr EQU 6 ;Swap file attribute (hidden+system) EmsPageSize EQU 16384 ;Size of EMS page FileBlockSize EQU 32768 ;Size of a file block StkSize EQU 128 ;Bytes in temporary stack lo EQU (WORD PTR 0) ;Convenient typecasts hi EQU (WORD PTR 2) ofst EQU (WORD PTR 0) segm EQU (WORD PTR 2) col EQU (BYTE PTR 0) row EQU (BYTE PTR 1) ;----------------------------------------------------------------------------- ;Variables in CS EmsDevice DB 'EMMXXXX0',0 ;Name of EMS device driver UsedEms DB 0 ;1 if swapping to EMS, 0 if to file BytesSwappedCS DD 0 ;Bytes to move during a swap EmsHandleCS DW 0 ;EMS handle FrameSegCS DW 0 ;Segment of EMS page window FileHandleCS DW 0 ;DOS file handle PrefixSegCS DW 0 ;Segment of base of program Status DW 0 ;ExecSwap status code LeftToSwap DD 0 ;Bytes left to move SaveSP DW 0 ;Original stack pointer SaveSS DW 0 ;Original stack segment PathPtr DD 0 ;Pointer to program to execute CmdPtr DD 0 ;Pointer to command line to execute ParasWeHave DW 0 ;Paragraphs allocated to process CmdLine DB 128 DUP(0) ;Terminated command line passed to DOS Path DB 64 DUP(0) ;Terminated path name passed to DOS FileBlock1 DB 16 DUP(0) ;FCB passed to DOS FileBlock2 DB 16 DUP(0) ;FCB passed to DOS EnvironSeg DW 0 ;Segment of environment for child CmdLinePtr DD 0 ;Pointer to terminated command line FilePtr1 DD 0 ;Pointer to FCB file FilePtr2 DD 0 ;Pointer to FCB file OrigInt21 DD 0 ;Previous $21 vector WindPos DW 0 ;Cursor position in window WindLo DW 0 ;Top left corner of window WindHi DW 0 ; and bottom right corner. WindAttr DB 0 ;Attribute with which to TempStack DB StkSize DUP(0) ;Temporary stack StackTop LABEL WORD ;Initial top of stack ;----------------------------------------------------------------------------- ;Macros MovSeg MACRO Dest,Src ;Set one segment register to another PUSH Src POP Dest ENDM MovMem MACRO Dest,Src ;Move from memory to memory via AX MOV AX,Src MOV Dest,AX ENDM InitSwapCount MACRO ;Initialize counter for bytes to swap MovMem LeftToSwap.lo,BytesSwappedCS.lo MovMem LeftToSwap.hi,BytesSwappedCS.hi ENDM SetSwapCount MACRO BlkSize ;Return CX = bytes to move this block LOCAL FullBlk ;...and reduce total bytes left to move MOV CX,BlkSize ;Assume we'll write a full block CMP LeftToSwap.hi,0 ;Is high word still non-zero? JNZ FullBlk ;Jump if so CMP LeftToSwap.lo,BlkSize ;Low word still a block or more? JAE FullBlk ;Jump if so MOV CX,LeftToSwap.lo ;Otherwise, move what's left FullBlk:SUB LeftToSwap.lo,CX ;Reduce number left to move SBB LeftToSwap.hi,0 ENDM NextBlock MACRO SegReg, BlkSize ;Point SegReg to next block to move MOV AX,SegReg ADD AX,BlkSize/16 ;Add paragraphs to next segment MOV SegReg,AX ;Next block to move MOV AX,LeftToSwap.lo OR AX,LeftToSwap.hi ;Bytes left to move? ENDM EmsCall MACRO FuncAH ;Call EMM and prepare to check result MOV AH,FuncAH ;Set up function INT 67h OR AH,AH ;Error code in AH ENDM DosCallAH MACRO FuncAH ;Call DOS subfunction AH MOV AH,FuncAH INT 21h ENDM DosCallAX MACRO FuncAX ;Call DOS subfunction AX MOV AX,FuncAX INT 21h ENDM InitSwapFile MACRO MOV BX,FileHandleCS ;BX = handle of swap file XOR CX,CX XOR DX,DX ;Start of file DosCallAX 4200h ;DOS file seek ENDM HaltWithError MACRO Level ;Halt if non-recoverable error occurs MOV AL,Level ;Set errorlevel DosCallAH 4Ch ENDM MoveFast MACRO ;Move CX bytes from DS:SI to ES:DI CLD ;Forward SHR CX,1 ;Convert to words REP MOVSW ;Move the words RCL CX,1 ;Get the odd byte, if any REP MOVSB ;Move it ENDM SetTempStack MACRO ;Switch to temporary stack MOV AX,OFFSET StackTop ;Point to top of stack MOV BX,CS ;Temporary stack in this code segment CLI ;Interrupts off MOV SS,BX ;Change stack MOV SP,AX STI ;Interrupts on ENDM ToDos MACRO ;Transfer control to DOS JMP DWORD PTR OrigInt21 ENDM ToApp MACRO ;Transfer control back to caller CLC ;Clear error flag RET 2 ;Return with flags intact ENDM ;----------------------------------------------------------------------------- ;procedure CheckCursor ; CheckCursor PROC NEAR PUSH BP MOV BP,SP ;Set up stack frame MOV AH,3 XOR BH,BH INT 10h ;Get cursor position MOV CX,WindLo CMP DH,CH ;Row above minimum? JAE CC1 ;Jump if so MOV DH,CH ;Force to minimum CC1: CMP DL,CL ;Col above minimum? JAE CC2 ;Jump is so MOV DL,CL ;Force to minimum CC2: MOV CX, WindHi CMP DH,CH ;Row below maximum? JBE CC3 ;Jump if so MOV DH,CH ;Force to maximum CC3: CMP DL,CL ;Col below maximum? JBE CC4 ;Jump if so MOV DL,CL ;Force to maximum CC4: MOV WindPos,DX ;Save current position MOV AH,2 XOR BH,BH INT 10h ;Make it so POP BP RET ;Return CheckCursor ENDP ;---------------------------------------------------------------------------- ;procedure InstallInt21 ; InstallInt21 PROC NEAR PUSH BP MOV BP,SP ;Set up stack frame ;Get the current Int21 vector DosCallAX 3521h ;ES:BX = vector MOV OrigInt21.ofst, BX ;Save as pointer in OrigInt21 MOV OrigInt21.segm, ES ;Install our Int21 handler PUSH DS MOV DX, SEG NewInt21 ;Segment of our handler MOV DS, DX MOV DX, OFFSET NewInt21 ;Offset of our handler DosCallAX 2521h ;Set it POP DS MOV NewInt21Addr, OFFSET NewInt21 MOV NewInt21Addr+2, SEG NewInt21 ;Show addr to caller POP BP RET ;Return InstallInt21 ENDP ;----------------------------------------------------------------------------- ;procedure RestoreInt21 ; RestoreInt21 PROC NEAR PUSH BP MOV BP,SP ;Set up stack frame PUSH DS LDS DX, OrigInt21 ;DS:DX = OrigInt21 DosCallAX 2521h ;Restore it POP DS POP BP RET ;Return RestoreInt21 ENDP ;----------------------------------------------------------------------------- ;procedure UpdateCsVars(Xlo, Ylo, Xhi, Yhi, Attr : Byte); ; UpdateCsVars PROC NEAR PUSH BP MOV BP,SP ;Set up stack frame ;Move passed values to CS variables MOV AX,[BP+12] DEC AX MOV BYTE PTR WindLo.Col, AL ;Lo(WindLo) = Xlo MOV AX,[BP+10] DEC AX MOV BYTE PTR WindLo.Row, AL ;Hi(WindLo) = Ylo MOV AX,[BP+8] DEC AX MOV BYTE PTR WindHi.Col,AL ;Lo(WindHi) = Xhi MOV AX, [BP+6] DEC AX MOV BYTE PTR WindHi.Row, AL ;Hi(WindHi) = Yhi MOV AX,[BP+4] MOV WindAttr, AL ;Get attribute POP BP RET 10 UpdateCsVars ENDP ;----------------------------------------------------------------------------- ;function ExecWithSwap(Path, CmdLine : string; ; Xlo, Ylo, Xhi, Yhi, Attr : Byte ) : Word; ExecWinWithSwap PROC FAR PUSH BP MOV BP,SP ;Set up stack frame ;Move variables to CS where we can easily access them later MOV Status,1 ;Assume failure LES DI,[BP+20] ;ES:DI -> Path MOV PathPtr.ofst,DI MOV PathPtr.segm,ES ;PathPtr -> path to execute LES DI,[BP+16] ;ES:DI -> CmdLine MOV CmdPtr.ofst,DI MOV CmdPtr.segm,ES ;CmdPtr -> command line string PUSH [BP+14] PUSH [BP+12] PUSH [BP+10] PUSH [BP+8] PUSH [BP+6] CALL UpdateCsVars ;Transfer parms to CS vars ;Make sure cursor is within window CALL CheckCursor ;Continue with swapping MOV SaveSP,SP ;Save stack position MOV SaveSS,SS MovMem BytesSwappedCS.lo,BytesSwapped.lo MovMem BytesSwappedCS.hi,BytesSwapped.hi MovMem EmsHandleCS,EmsHandle MovMem FrameSegCS,FrameSeg MovMem FileHandleCS,FileHandle MovMem PrefixSegCS,PrefixSeg InitSwapCount ;Initialize bytes LeftToSwap ;Install our Int21 handler CALL InstallInt21 ;Check for swapping to EMS or file CMP EmsAllocated,0 ;Check flag for EMS method JZ NotEms ;Jump if EMS not used JMP WriteE ;Swap to EMS NotEms: CMP FileAllocated,0 ;Check flag for swap file method JNZ WriteF ;Swap to file JMP ESDone ;Exit if no swapping method set ;Write to swap file WriteF: MovSeg DS,CS ;DS = CS InitSwapFile ;Seek to start of swap file JNC EF0 ;Jump if success JMP ESDone ;Exit if error EF0: SetSwapCount FileBlockSize ;CX = bytes to write MOV DX,OFFSET FirstToSave ;DS:DX -> start of region to save DosCallAH 40h ;File write JC EF1 ;Jump if write error CMP AX,CX ;All bytes written? JZ EF2 ;Jump if so EF1: JMP ESDone ;Exit if error EF2: NextBlock DS,FileBlockSize ;Point DS to next block to write JNZ EF0 ;Loop if bytes left to write MOV UsedEms,0 ;Flag we used swap file for swapping DosCallAH 45h ;DUP handle JC EF2a ;Jump if failed MOV BX,AX ;Prepare to close dup'ed handle DosCallAH 3Eh ;Flush swap file EF2a: JMP SwapDone ;Done swapping out ;Write to EMS WriteE: MOV ES,FrameSeg ;ES -> page window MOV DX,EmsHandle ;DX = handle of our EMS block EmsCall 47h ;Save EMS context XOR BX,BX ;BX = initial logical page MovSeg DS,CS ;DS = CS EE0: XOR AL,AL ;Physical page 0 EmsCall 44h ;Map physical page JZ EE1 ;Jump if success JMP ESDone ;Exit if error EE1: SetSwapCount EmsPageSize ;CX = Bytes to move XOR DI,DI ;ES:DI -> base of EMS page MOV SI,OFFSET FirstToSave ;DS:SI -> region to save MoveFast ;Move CX bytes from DS:SI to ES:DI INC BX ;Next logical page NextBlock DS,EmsPageSize ;Point DS to next page to move JNZ EE0 ;Loop if bytes left to move EmsCall 48h ;Restore EMS context MOV UsedEms,1 ;Flag we used EMS for swapping ;Shrink memory allocated to this process SwapDone:MOV AX,PrefixSegCS MOV ES,AX ;ES = segment of our memory block DEC AX MOV DS,AX ;DS = segment of memory control block MOV CX,DS:[0003h] ;CX = current paragraphs owned MOV ParasWeHave,CX ;Save current paragraphs owned SetTempStack ;Switch to temporary stack MOV AX,OFFSET FirstToSave+15 MOV CL,4 SHR AX,CL ;Convert offset to paragraphs ADD BX,AX SUB BX,PrefixSegCS ;BX = new paragraphs to keep DosCallAH 4Ah ;SetBlock JNC EX0 ;Jump if successful JMP EX5 ;Swap back and exit ;Set up parameters and call DOS Exec EX0: MOV AX,ES:[002Ch] ;Get environment segment MOV EnvironSeg,AX MovSeg ES,CS ;ES = CS LDS SI,PathPtr ;DS:SI -> path to execute MOV DI,OFFSET Path ;ES:DI -> local ASCIIZ copy CLD LODSB ;Read current length CMP AL,63 ;Truncate if exceeds space set aside JB EX1 MOV AL,63 EX1: MOV CL,AL XOR CH,CH ;CX = bytes to copy REP MOVSB XOR AL,AL STOSB ;ASCIIZ terminate LDS SI,CmdPtr ;DS:SI -> Command line to pass MOV DI,OFFSET CmdLine ;ES:DI -> Local terminated copy LODSB CMP AL,126 ;Truncate command if exceeds space JB EX2 MOV AL,126 EX2: STOSB MOV CL,AL XOR CH,CH ;CX = bytes to copy REP MOVSB MOV AL,0DH ;Terminate with ^M STOSB MovSeg DS,CS ;DS = CS MOV SI,OFFSET CmdLine MOV CmdLinePtr.ofst,SI MOV CmdLinePtr.segm,DS ;Store pointer to command line INC SI MOV DI,OFFSET FileBlock1 MOV FilePtr1.ofst,DI MOV FilePtr1.segm,ES ;Store pointer to filename 1, if any DosCallAX 2901h ;Parse FCB MOV DI,OFFSET FileBlock2 MOV FilePtr2.ofst,DI MOV FilePtr2.segm,ES ;Store pointer to filename 2, if any DosCallAX 2901h ;Parse FCB MOV DX,OFFSET Path MOV BX,OFFSET EnvironSeg DosCallAX 4B00h ;Exec JC EX3 ;Jump if error in DOS call XOR AX,AX ;Return zero for success EX3: MOV Status,AX ;Save DOS error code ;Set up temporary stack and reallocate original memory block SetTempStack ;Set up temporary stack MOV ES,PrefixSegCS MOV BX,ParasWeHave DosCallAH 4Ah ;SetBlock JNC EX4 ;Jump if no error HaltWithError 0FFh ;Must halt if failure here EX4: InitSwapCount ;Initialize LeftToSwap ;Check which swap method is in use EX5: CMP UsedEms,0 JZ ReadF ;Jump to read back from file JMP ReadE ;Read back from EMS ;Read back from swap file ReadF: MovSeg DS,CS ;DS = CS InitSwapFile ;Seek to start of swap file JNC EF3 ;Jump if we succeeded HaltWithError 0FEh ;Must halt if failure here EF3: SetSwapCount FileBlockSize ;CX = bytes to read MOV DX,OFFSET FirstToSave ;DS:DX -> start of region to restore DosCallAH 3Fh ;Read file JNC EF4 ;Jump if no error HaltWithError 0FEh ;Must halt if failure here EF4: CMP AX,CX JZ EF5 ;Jump if full block read HaltWithError 0FEh ;Must halt if failure here EF5: NextBlock DS,FileBlockSize ;Point DS to next page to read JNZ EF3 ;Jump if bytes left to read JMP ESDone ;We're done ;Copy back from EMS ReadE: MOV DX,EmsHandleCS ;DX = handle of our EMS block EmsCall 47h ;Save EMS context for next time MOV DS,FrameSegCS ;DS -> page window XOR BX,BX ;BX = initial logical page MovSeg ES,CS ;ES = CS EE3: XOR AL,AL ;Physical page 0 EmsCall 44h ;Map physical page JZ EE4 ;Jump if success HaltWithError 0FDh ;Must halt if failure here EE4: SetSwapCount EmsPageSize ;CX = Bytes to move XOR SI,SI ;DS:SI -> base of EMS page MOV DI,OFFSET FirstToSave ;ES:DI -> region to restore MoveFast ;Move CX bytes from DS:SI to ES:DI INC BX ;Next logical page NextBlock ES,EmsPageSize ;Point ES to next page to move JNZ EE3 ;Jump if so EmsCall 48h ;Restore EMS context ESDone: CLI ;Switch back to original stack MOV SS,SaveSS MOV SP,SaveSP STI CALL RestoreInt21 ;Restore original int21 MOV AX,SEG DATA MOV DS,AX ;Restore DS MOV AX,Status ;Return status POP BP RET 18 ;Remove parameters and return ExecWinWithSwap ENDP ;--------------------------------------------------------------------------- ;procedure NewInt21 ; Handle interrupt 21 to trap output calls NewInt21 PROC FAR STI CMP AH,2 ;Just get functions that go to StdOut JZ DispOut CMP AH,6 JZ DirectOut CMP AH,9 JZ StringOut CMP AH,40h ;Or maybe to StdErr JZ BlockOut ToDos ;----------- DispOut: ;DOS function 2 PUSH AX MOV AL,DL ;Character to write in AL CALL WriteChar ;Write via video BIOS POP AX ToApp ;Return successfully ;----------- DirectOut: ;DOS function 6 CMP DL,0FFh ;Console input? JNZ DispOut ;Jump if not ToDos ;Else transfer to DOS ;------------ StringOut: ;DOS function 9 PUSH AX ;Save AX PUSH BX ;Save string index MOV BX,DX ;DS:BX -> string StringOut1: MOV AL,[BX] ;AL = next character to write CMP AL,'$' ;Terminator? JZ StringOut2 ;Exit if so CALL WriteChar ;Write it INC BX ;Next character JMP StringOut1 ;Loop StringOut2: POP BX POP AX ToApp ;Back to application ;------------ BlockOut: ;DOS function 40h CMP BX,1 ;To StdOut? JZ BlockOut1 ;Jump if so CMP BX,2 ;To StdErr? JZ BlockOut1 ;Jump if so ToDos ;Else let DOS handle it BlockOut1: JCXZ BlockOut3 ;Get out if none to write PUSH AX PUSH BX PUSH CX ;Save loop counter MOV BX,DX ;DS:BX -> stuff to write BlockOut2: MOV AL,[BX] ;Next character to write CALL WriteChar ;Write it INC BX ;Next index LOOP BlockOut2 ;Loop for all the characters POP CX POP BX POP AX MOV AX,CX ;Wrote all the characters BlockOut3: ToApp ;Back to application NewInt21 ENDP ;------------ ; Write a character to current position via BIOS ; Entry: AL is character to write ; Must preserve all but AX WriteChar proc near PUSH bp ;some versions of int 10 BIOS trash BP PUSH bx PUSH cx PUSH dx PUSH ds CMP al,7 ;Bell character? JZ BiosWriteDone ;Don't write MOV dx,WindPos ;Current cursor pos in DX CMP al,8 ;Backspace? JZ BackSpace CMP al,9 ;Tab? JZ Tab CMP al,10 ;Line feed? JZ LineFeed CMP al,13 ;Carriage return? JZ Carriage CALL WriteOne ;Write one normal character BiosSetCursor: ;Position cursor XOR bh,bh MOV ah,2 INT 10h MOV WindPos,dx ;Save new cursor position BiosWriteDone: POP ds POP dx POP cx POP bx POP bp RET Carriage: MOV dl,WindLo.col ;Move to left edge JMP BiosSetCursor LineFeed: CMP dh,WindHi.row ;Room to increment row? JB LineFeed1 MOV ax,0601h ;Scroll up one line MOV cx,WindLo MOV dx,WindHi MOV bh,WindAttr INT 10h JMP BiosWriteDone LineFeed1: INC dh ;Increment row JMP BiosSetCursor ;Set cursor Tab: MOV cl,dl SUB cl,WindLo.Col ;Characters beyond left edge ADD cl,8 AND cl,0F8h ;To next tab stop ADD cl,WindLo.Col ;Window coords SUB cl,dl ;Spaces to write XOR ch,ch ;CX = spaces to write Tab1: MOV al,20h ;Write spaces PUSH cx CALL WriteOne ;One at a time XOR bh,bh MOV ah,2 INT 10h MOV WindPos,dx ;Save new cursor position POP cx LOOP Tab1 ;Do all of them JMP BiosWriteDone BackSpace: CMP dl,WindLo.col ;Beyond left edge? JBE BiosWriteDone ;Exit if not DEC dl ;One left XOR bh,bh MOV ah,2 ;Position cursor INT 10h MOV WindPos,dx MOV cx,1 ;Write character MOV bl,WindAttr MOV ax,0920h ;Write a space INT 10h JMP BiosWriteDone ;Done now WriteChar endp ;--------------- ; Write one character and update cursor variable WriteOne proc near MOV cx,1 ;Write character MOV bl,WindAttr XOR bh,bh MOV ah,9 INT 10h CMP dl,WindHi.col ;Below right border? JB IncCol ;If so, just increment column CMP dh,WindHi.row ;Room for CR/LF? JB IncRow ;Jump if so MOV ax,0601h ;Scroll up one line MOV cx,WindLo MOV dx,WindHi MOV bh,WindAttr INT 10h DEC dh ;Compensate for inc to follow IncRow: INC dh ;Next row MOV dl,WindLo.col ;First col DEC dl ;Compensate for inc to follow IncCol: INC dl ;Increment column RET WriteOne endp ;----------------------------------------------------------------------------- ;Label marks first location to swap EVEN FirstToSave: ;----------------------------------------------------------------------------- ;function AllocateSwapFile : Boolean; AllocateSwapFile PROC NEAR MOV CX,FileAttr ;Attribute for swap file MOV DX,OFFSET SwapName+1 ;DS:DX -> ASCIIZ swap name DosCallAH 3Ch ;Create file MOV FileHandle,AX ;Save handle assuming success MOV AL,0 ;Assume failure JC ASDone ;Failed if carry set INC AL ;Return true for success ASDone: RET AllocateSwapFile ENDP ;----------------------------------------------------------------------------- ;procedure DeallocateSwapFile; DeallocateSwapFile PROC NEAR MOV BX,FileHandle ;Handle of swap file DosCallAH 3Eh ;Close file XOR CX,CX ;Normal attribute MOV DX,OFFSET SwapName+1 ;DS:DX -> ASCIIZ swap name DosCallAX 4301h ;Set file attribute DosCallAH 41h ;Delete file RET DeallocateSwapFile ENDP ;----------------------------------------------------------------------------- ;function EmsInstalled : Boolean; EmsInstalled PROC FAR PUSH DS MovSeg DS,CS ;DS = CS MOV DX,OFFSET EmsDevice ;DS:DX -> EMS driver name DosCallAX 3D02h ;Open for read/write POP DS MOV BX,AX ;Save handle in case one returned MOV AL,0 ;Assume FALSE JC EIDone DosCallAH 3Eh ;Close file MOV AL,1 ;Return TRUE EIDone: RET EmsInstalled ENDP ;----------------------------------------------------------------------------- ;function EmsPageFrame : Word; EmsPageFrame PROC FAR EmsCall 41h ;Get page frame MOV AX,BX ;AX = segment JZ EPDone ;Done if Error = 0 XOR AX,AX ;Else segment = 0 EPDone: RET EmsPageFrame ENDP ;----------------------------------------------------------------------------- ;function AllocateEmsPages(NumPages : Word) : Word; AllocateEmsPages PROC FAR MOV BX,SP ;Set up stack frame MOV BX,SS:[BX+4] ;BX = NumPages EmsCall 43h ;Allocate EMS MOV AX,DX ;Assume success JZ APDone ;Done if not 0 MOV AX,0FFFFh ;$FFFF for failure APDone: RET 2 ;Remove parameter and return AllocateEmsPages ENDP ;----------------------------------------------------------------------------- ;procedure DeallocateEmsHandle(Handle : Word); DeallocateEmsHandle PROC FAR MOV BX,SP ;Set up stack frame MOV DX,SS:[BX+4] ;DX = Handle EmsCall 45h ;Deallocate EMS RET 2 ;Remove parameter and return DeallocateEmsHandle ENDP ;----------------------------------------------------------------------------- ;function DefaultDrive : Char; DefaultDrive PROC FAR DosCallAH 19h ;Get default drive ADD AL,'A' ;Convert to character RET DefaultDrive ENDP ;----------------------------------------------------------------------------- ;function DiskFree(Drive : Byte) : LongInt; DiskFree PROC FAR MOV BX,SP ;Set up stack frame MOV DL,SS:[BX+4] ;DL = Drive to check DosCallAH 36h ;Get disk space MOV DX,AX ;Return 0FFFFFFFFh for failure CMP AX,0FFFFh ;Bad drive number? JZ DFDone ;Jump if so MUL CX ;AX = bytes/cluster MUL BX ;DX:AX = bytes free DFDone: RET 2 ;Remove parameter and return DiskFree ENDP ;----------------------------------------------------------------------------- CODE ENDS END